Precombustion Fuel/Air Distribution in a Stratified Charge Engine Using Laser Raman Spectroscopy

The application of cw laser Raman spectroscopy to determine precombustion fuel/air distribution in a motored, direct-injected stratified charge (DISC) engine has been demonstrated. The primary objective of the study was to obtain point measurements of the mean, gas-phase fuel/air ratio across a diameter in the combustion chamber for a single set of engine operating parameters. A secondary objective was to obtain flow visualization records of the injection-mixing process for both liquid- and gas-phase fuel injection.

Results of the study showed that large spatial variations in the fuel/air ratio occur in the cylinder during and after fuel injection. Near top-dead-center, fuel/air mixing was nearly complete, but the distribution across the cylinder diameter still exhibited a region of relatively low fuel concentration.